1. Field of the Invention
The invention described herein relates to shock absorbers for hinged doors; and more particularly to a shock absorber system for ice condenser doors in a nuclear reactor power plant.
2. Description of the Prior Art
The major components of a nuclear reactor power plant including the reactor, pumps, steam generators and connecting piping are located in a concrete containment structure. Coolant circulated through the reactor by the pumps absorbs heat from the fission process and as this heated coolant is passed through the steam generators, the heat is transferred to a secondary circuit which then provides steam for driving a turbo-generator which generates electric power. During the course of circulating such coolant into heat exchange relationship with the reactor fuel elements, gases and particles in the coolant may become radioactive and cannot be permitted to escape to the atmosphere. It therefore is apparent that in the unlikely event of rupture of the primary coolant piping, the released coolant flashes into steam and the released radioactive particles must be contained in the reactor containment. To accommodate the consequent rise in pressure inside the reactor containment and to prevent such escape of radioactive particles to the atmosphere, one well known method includes condensing the steam by passing it over ice located in a compartment positioned around the inside walls of the reactor containment.
U.S. patent application Ser. No. 435,903, filed Dec. 23, 1973 by S. J. Weems et al. entitled "Nuclear Reactor Condenser Door Arrangement", assigned to the same assignee as the present invention, discloses different designs and features of an ice condenser compartment used for this purpose. As shown and described therein, doors are located in the bottom and at the top of the ice condenser compartment. Should a steam break occur, such as complete rupture of the largest coolant pipe, steam released by the coolant generates a pressure which opens the bottom doors thus permitting steam including radioactive particles to enter the compartment and condense on the ice located therein. After the initial pressure surge, the doors must be capable of returning to a normally closed position without being warped or otherwise bent in order to continue performing their flow metering function of regulating and proportioning the long term steam boil-off due to decay heat.
Present designs of doors which conventionally measure 84-92 inches high, 42 inches wide, and 8 inches thick will generate about 30,000 to 50,000 foot pounds of energy when the surface of a door facing the reactor compartment is exposed to a pressure of about 12 psi. This pressure is sufficient to open the doors at a high velocity and an important reason for absorbing the door energy with a shock absorber that limits the forces is that otherwise the forces imposed by the swinging door on the ice condenser compartment door frames and the adjacent wall may well damage the structural components sufficiently as to require extensive repairs to the structure.
A shock absorber was initially designed which adequately performed the intended absorbing function, but which was complicated and expensive to manufacture. It is described in detail in application Ser. No. 459,450, by Joseph F. Meier et al., filed Apr. 9, 1974, and assigned to the Westinghouse Electric Corporation. The Meier et al. shock absorber basically comprised a phenolic foam with rigid-brittle type failure in compression. However, as such foam disintegrates into very small particles during compression, it had a potential for draining to the containment sump and blocking flow areas. The foam was therefore encased in a specially manufactured plastic bag, and the bag enclosed in a knitted wire mesh bag. Further, to provide necessary redundancy and to preserve the geometry of the foam during compression, stainless steel sheet metal was used to cover the absorber impact face and the top and bottom surfaces of the absorber. This design presented a complicated series of components which, although meeting the functional criteria, was complex and costly. Also, the size and shape of the prior absorber made it somewhat difficult to install and would be difficult to remove and dispose of subsequent to an accident.
A shock absorber which eliminates these concerns while retaining the positive functional aspects is disclosed herein. It constitutes an improvement in the design and operation of the shock absorber disclosed in the above discussed Meier et al. application.